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Hawaiian Islands Synoptic Discussion and Guidance

767
FXHW60 PHFO 241422
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
410 AM HST MON NOV 24 2014

.SYNOPSIS...
A WEAKENING COLD FRONT WILL CONTINUE TO MOVE ACROSS THE SMALLER
ISLANDS THIS MORNING...THEN STALL AND QUICKLY DISSIPATE NEAR THE
BIG ISLAND LATER THIS AFTERNOON. SHOWERS WILL BRING MAINLY LIGHT TO
MODERATE RAIN...BUT A FEW BRIEF PERIODS OF LOCALIZED HEAVY RAIN ARE
CERTAINLY POSSIBLE...ESPECIALLY OVER MOUNTAIN AREAS OF OAHU AND MAUI
COUNTY. COOLER...DRIER AIR AND STRONGER NORTHERLY WINDS WILL FOLLOW
THE FRONT...WITH WINDS TURNING NORTH LATER THIS AFTERNOON AND
NORTHEAST BY TUESDAY. LOCALLY BREEZY TRADES WILL THEN CONTINUE
THROUGH THE WEEK...BRINGING BRIEF WINDWARD AND MAUKA SHOWERS.

&&

.DISCUSSION...
A SHARP MID/UPPER LVL TROUGH CONTINUES TO MIGRATE E AT ABOUT 30 MPH
ACROSS THE N CENTRAL PACIFIC...WHILE A SFC COLD FRONT BOUNDARY
MOVING ACROSS THE W HALF OF THE ISLAND CHAIN. A BAND OF SHOWERS WITH
PERIODS OF BRIEF LOCALIZED HEAVY RAIN MARKS THE LEADING EDGE OF THE
FRONT...WHICH WAS OBSERVED ON RADAR DATA MOVING ACROSS E KAUAI AT 3
AM HST. HEAVY DOWNPOURS WERE AFFECTING THE AREA AROUND KOKEE STATE
PARK AND WAINIHA WITH RAINFALL RATES OF 2 TO 3 INCHES AN HOUR...FOR
WHICH A FLOOD ADVISORY WAS ISSUED. THE BAND OF SHOWERS IS MOVING
E/SE AT 20 TO 25 MPH...AND RAIN COVERAGE SHOULD GRADUALLY DECREASE
ACROSS KAUAI THROUGH THE EARLY MORNING HOURS. THE FRONT WILL
CONTINUE TO MOVE ACROSS THE KAUAI CHANNEL AND REACH OAHU BY MID
MORNING...WITH PERIODS OF CLOUDS...MODERATE RAIN...AND BRIEF HEAVY
DOWNPOURS POSSIBLE.

MEANWHILE...SFC HIGH PRESSURE REMAINS CENTERED FAR NE OF THE
AREA...WITH AN ASSOCIATED SFC RIDGE AXIS STRETCHING TO ABOUT 200
MILES SE OF THE BIG ISLAND. THIS SYNOPTIC SETUP IS NOW SHIFTING
WINDS AROUND THE BIG ISLAND TO A MORE S TO SW FLOW AS THE FRONT
CONTINUES TO MOVE DOWN THE ISLAND CHAIN TODAY. THE BULK OF THE MODEL
GUIDANCE REMAINS IN FAIR AGREEMENT REGARDING THE OVERALL SOLUTION
FOR THE FROPA...MOVING ACROSS OAHU AND MAUI COUNTY THROUGH THE REST
OF THE MORNING HOURS...THEN STALLING AND QUICKLY BREAKING DOWN
AROUND THE BIG ISLAND THIS AFTERNOON. A RELATIVELY DRY PROFILE FOR
THE MID LVLS...AND PWATS AROUND 1 INCH IN THE 12Z LIHUE SOUNDING
SUGGEST THAT SHOWERS SHOULD REMAIN LIGHT TO MODERATE IN GENERAL. BUT
A FEW BRIEF LOCALIZED DOWNPOURS CAN NOT BE RULED OUT...MAINLY OVER
MOUNTAIN AREAS OF OAHU AND MAUI COUNTY THROUGH THE REST OF THIS
MORNING.

AS THE FRONT DISSIPATES AND HIGH PRESSURE RE-ESTABLISHES IN THE WAKE
OF THE AFOREMENTIONED UPPER LEVEL TROUGH...WINDS BEHIND THE FROPA
WILL STRENGTHEN AND TURN FROM THE N THIS LATER THIS AFTERNOON.
OVERALL CONDITIONS WILL BECOME MUCH DRIER AND GUSTY LATE TONIGHT
THROUGH TUE...WITH DEWPOINTS DROPPING INTO THE UPPER 50S.

THE STRONG HIGH PRESSURE N OF THE ISLANDS WILL KEEP A MODERATE TO
LOCALLY FRESH TRADE WIND REGIME ACROSS THE AREA THROUGH THE REST OF
THE WEEK. LOW LEVEL MOISTURE SHOULD GRADUALLY RECOVER DURING THE
SECOND HALF OF THE WEEK WITH SHOWER ACTIVITY SHIFTING OVER WINDWARD
AND MAUKA AREAS.


&&

.AVIATION...
A COLD FRONT MOVING ACROSS KAUAI AS OF 24/12Z WILL CONTINUE MOVING
SOUTHEAST ACROSS THE STATE TODAY...REACHING OAHU AROUND SUNRISE AND
MAUI COUNTY BY MIDDAY. AREAS OF MVFR CONDITIONS WILL BE LIKELY
WITHIN A BAND OF CLOUDS AND SHOWERS ALONG THE FRONT...WITH
ISOLATED/BRIEF IFR CONDITIONS POSSIBLE. AIRMET SIERRA FOR MOUNTAIN
OBSCURATION HAS BEEN POSTED ACROSS KAUAI...AND MAY BECOME NECESSARY
FOR OAHU AND PARTS OF MAUI COUNTY DURING THE DAY. THE FRONT WILL
WEAKEN AS IT APPROACHES THE BIG ISLAND LATE THIS AFTERNOON INTO
THIS EVENING...BUT DEVELOPING NORTHERLY FLOW WILL LIKELY CAUSE AN
INCREASE IN SHOWER ACTIVITY AND THE POTENTIAL FOR MOUNTAIN
OBSCURATION ALONG THE SLOPES OF THE HAMAKUA COAST.

A TROUGH ALOFT WILL ALSO BE PASSING ACROSS THE STATE TODAY. MODELS
INDICATE SOME POTENTIAL FOR HIGH LEVEL TURBULENCE AS THIS TROUGH
MOVES THROUGH...BUT GIVEN THE LACK OF ANY TURB REPORTS FROM
AIRCRAFT TRANSITING BETWEEN HAWAII AND ASIA HAVE ONLY INCLUDED A
MENTION OF ISOLATED MOD TURB IN THE AIRMET TANGO BULLETIN AT THIS
TIME.

&&

.MARINE...
THE COMBINATION OF STRONG NORTHERLY WINDS BEHIND A COLD FRONT AND A
LARGE NORTHWEST SWELL WILL BRING SMALL CRAFT ADVISORY CONDITIONS
OVER MOST MARINE ZONES THROUGH 6 AM HST TUESDAY. THEN BY WEDNESDAY...
STRONG NORTHEASTERLY WINDS WILL LIKELY BRING ANOTHER ROUND OF SMALL
CRAFT ADVISORY CONDITIONS OVER THE TYPICALLY WINDIER WATERS AROUND
THE BIG ISLAND AND MAUI COUNTY.

THE CURRENT NORTH-NORTHWEST SWELL WILL BRING SURF HEIGHTS TO
ADVISORY THROUGH TUESDAY FOR NORTH FACING SHORES OF ALL SMALLER
ISLANDS...AND FOR WEST FACING SHORES OF KAUAI COUNTY. BREEZY TRADE
WINDS LATER IN THE WEEK WILL PRODUCE CHOPPY SURF ALONG EAST FACING
SHORES...BUT IS EXPECTED TO REMAIN BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU-MOLOKAI-MAUI
WINDWARD WEST-WINDWARD HALEAKALA.

WIND ADVISORY UNTIL 6 PM HST THIS EVENING FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-KAIWI CHANNEL-MAUI
COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND WINDWARD WATERS.

SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM HST TUESDAY
FOR BIG ISLAND SOUTHEAST WATERS.

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...JACOBSON




Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office